Abstract: A mode coupling device is provided for coupling co-propagating modes in an optical waveguide to provide a gain flattening filter for use with an optical amplifier such as an erbium-doped fiber amplifier. The mode coupling device includes a plurality of long period grating sections having equal spatial periods, with adjacent grating sections separated by an interval of less than 10 periods in length. Also provided is a method for manufacturing the mode coupling device, including a method for determining the parameters of the device and a method for fine tuning the device to provide a loss spectrum closely matching the output spectrum of the optical amplifier. The mode coupling device is useful for flattening the gain of the optical amplifier.

Abstract: A mode coupling device is provided for coupling co-propagating modes in an optical waveguide to provide a gain flattening filter for use with an optical amplifier such as an erbium-doped fiber amplifier. The mode coupling device includes a plurality of long period grating sections having equal spatial periods, with adjacent grating sections separated by an interval of less than 10 periods in length. Also provided is a method for manufacturing the mode coupling device, including a method for determining the parameters of the device and a method for fine tuning the device to provide a loss spectrum closely matching the output spectrum of the optical amplifier. The mode coupling device is useful for flattening the gain of the optical amplifier.

Abstract: An optical fiber having a carbonized or diamond-like coating and a method for manufacturing same is provided. The carbonized or diamond-like coating is formed by modifying the polymer coatings typically used by optical fiber manufacturers to protect the optical fiber from mechanical and environmental damage. The carbonized coating is formed by heating the fiber at a controlled temperature for a predetermined period of time to carbonize the polymer layers. This carbonization results in a reduced fiber diameter resulting in excellent adhesion of the carbonized or diamond-like coating without substantially decreasing the mechanical strength of the optical fiber. The carbonized coating also assists in mounting the optical fiber, especially where adhesion of the coating to the cladding of the fiber is important, such as in a device where strain is applied to a fiber grating to tune the photosensitivity of the grating.

Abstract: A series of relatively low reflectivity Bragg gratings are used to stabilize the power and wavelength output of a semiconductor laser. The series of Bragg gratings may be formed in the core of a waveguide, typically either an optical fiber or a planar waveguide circuit, by illuminating the core of the fiber or waveguide through a mask directly through a polymer coating of the fiber or, in the case of a planar waveguide, though the outer layers of the waveguide. The reflectivity of each Bragg grating in the series is less than the reflectivity of the output facet of the laser. The Bragg grating nearest the laser may be located within the coherence distance of the laser. The Bragg gratings may be separated by uniform distance, or the separation between gratings may be non-uniform. Additionally, the gratings may have the same or different periods and reflectivities.

Abstract: A method of making a phase mask for imposing on light transmitted therethrough an interference pattern. The method comprises various steps including the step of depositing a solidifiable material on a substrate with a first surface relief pattern. The solidifiable material is selected so that the phase mask is at least half as transmissive as it is absorptive of light characterized by a spectral line having a wavelength between 275 and 390 nm. The material is solidified and removed from the substrate so as to yield the phase mask with a second surface relief pattern complementary to the first surface relief pattern.

Abstract: The present invention relates to a method for changing the refractive index in an element comprising germanium silicate glass by irradiating the germanium silicate glass with laser radiation having an associated wavelength in the range of 270 nm to 390 nm for exciting an absorption band in the glass centered at 330 nm. The element may be polymer coated in which instance the glass is irradiated through the polymer coating. In addition, the glass may have been exposed to a hydrogen atmosphere before being irradiated. In either instance, the laser radiation is directed at an angle to the surface of the element or along an optical axis of the element or both. The element may comprise a portion of an optical light guide, such as an optical fiber, or such as an integrated optical waveguide.

Abstract: A grating is induced in the core of a hydrogen-loaded high-germanium-content optical fiber using near-UV (275 nm-390 nm) laser light. An interference is generated at the core using a molded polymer phase mask with a square wave surface relief pattern. The light is directed through the phase mask, through a protective fiber coating, through the cladding, and into the core. The phase mask generates an interference pattern with a period half that of the surface relief pattern. Index of refraction changes occur at the bright fringes of the interference pattern--thus creating the grating. Advantages over existing mid-UV technology include lower fabrication costs for phase masks, simplified grating induction since fiber coatings do not need to be removed, and reduced infrared absorption caused by grating formation fiber.

Abstract: A grating is induced in the core of a hydrogen-loaded high-germanium-content optical fiber using near-UV (275 nm-390 nm) laser light. An interference pattern is generated at the core using a molded polymer phase mask with a square wave surface relief pattern. The light is directed through the phase mask, through a protective fiber coating, through the cladding, and into the core. The phase mask generates an interference pattern with a period half that of the surface relief pattern. Index of refraction changes occur at the bright fringes of the interference pattern--thus creating the grating. Advantages over existing mid-UV technology include lower fabrication costs for phase masks, simplified grating induction since fiber coatings do not need to be removed, and reduced infrared absorption caused by grating formation in the fiber.

Abstract: A grating is induced in the core of a hydrogen-loaded high-germanium-content optical fiber using near-UV (275 nm-390 nm) laser light. An interference pattern is generated at the core using a molded polymer phase mask with a square wave surface relief pattern. The light is directed through the phase mask, through a protective fiber coating, through the cladding, and into the core. The phase mask generates an interference pattern with a period half that of the surface relief pattern. Index of refraction changes occur at the bright fringes of the interference pattern--thus creating the grating. Advantages over existing mid-UV technology include lower fabrication costs for phase masks, simplified grating induction since fiber coatings do not need to be removed, and reduced infrared absorption caused by grating formation in the fiber.